Objective:Avidly phagocytosed hemozoin (malarial pigment)alters several functions of human monocytes and stimulates generation of several cytokines.Recently,we showed that phagocytosis of hemozoin by human mono-cytes increases expression and activity of matrix metalloproteinase-9,a proteolytic enzyme available in specific gelatinase granules,which contain several enzymes including lysozyme.Present work investigated active lyso-zyme release after phagocytosis of hemozoin and its dependence on production of tumor necrosis factor alpha. Methods:After phagocytosis of hemozoin,hemozoin-containing trophozoites or control meals (opsonized non-parasitized red blood cells and latex particles),monocyte supatants were monitored for 2 hours,in presence of blocking anti-human tumor necrosis factor alpha antibodies or recombinant human tumor necrosis factor alpha cytokine in selected experiments.Lysozyme release was evaluated by a specific spectrometric assay measuring lysozyme activity after coincubation of cell supatants with suspensions of Mycrococcus Lysodeikticus,while levels of soluble tumor necrosis factor alpha were analyzed by specific enzyme-linked immunodsorbent assay. Results:Levels of lysozyme activity and soluble tumor necrosis factor alpha protein were increased in hemozo-in-or trophozoites-laden monocytes supatants.Phagocytosis per se (control meals)also increased lysozyme release,but levels were significantly lower than those obtained after phagocytosis of hemozoin or trophozoites. Interestingly,all effects on lysozyme release observed after phagocytosis were abrogated by blocking anti-human tumor necrosis factor alpha antibodies,while they were mimicked by recombinant human tumor necrosis factor alpha cytokine.Conclusions:Present work shows that phagocytosis of hemozoin promotes monocyte degranula-tion and enhances active lysozyme release.The effect requires tumor necrosis factor alpha mediation.